Re: [PATCH] zram: propagate error to user
Hello,
On (03/10/14 11:01), Minchan Kim wrote:
> Hello Sergey,
>
> On Sun, Mar 09, 2014 at 07:58:51PM +0300, Sergey Senozhatsky wrote:
> > Hello Minchan,
> >
> > On (03/07/14 18:51), Minchan Kim wrote:
> > > Hello Sergey!
> > >
> > > On Fri, Mar 07, 2014 at 12:20:45PM +0300, Sergey Senozhatsky wrote:
> > > > On (03/07/14 10:56), Minchan Kim wrote:
> > > > > When we initialized zcomp with single, we couldn't change
> > > > > max_comp_streams without zram reset but current interface doesn't
> > > > > show any error to user and even it changes max_comp_streams's value
> > > > > without any effect so it would make user very confusing.
> > > > >
> > > > > This patch prevents max_comp_streams's change when zcomp was
> > > > > initialized as single zcomp and emit the error to user(ex, echo).
> > > > >
> > > > > Signed-off-by: Minchan Kim
> > > > > ---
> > > > > Documentation/blockdev/zram.txt | 9 +
> > > > > drivers/block/zram/zcomp.c | 10 +-
> > > > > drivers/block/zram/zcomp.h | 4 ++--
> > > > > drivers/block/zram/zram_drv.c | 15 +++
> > > > > 4 files changed, 23 insertions(+), 15 deletions(-)
> > > > >
> > > > > diff --git a/Documentation/blockdev/zram.txt
> > > > > b/Documentation/blockdev/zram.txt
> > > > > index 2604ffed51db..0595c3f56ccf 100644
> > > > > --- a/Documentation/blockdev/zram.txt
> > > > > +++ b/Documentation/blockdev/zram.txt
> > > > > @@ -37,10 +37,11 @@ Note:
> > > > > In order to enable compression backend's multi stream support
> > > > > max_comp_streams
> > > > > must be initially set to desired concurrency level before ZRAM device
> > > > > initialisation. Once the device initialised as a single stream
> > > > > compression
> > > > > -backend (max_comp_streams equals to 0) changing the value of
> > > > > max_comp_streams
> > > > > -will not take any effect, because single stream compression backend
> > > > > implemented
> > > > > -as a special case and does not support dynamic max_comp_streams.
> > > > > Only multi
> > > > > -stream backend supports dynamic max_comp_streams adjustment.
> > > > > +backend (max_comp_streams equals to 1), you will see error if you
> > > > > try to change
> > > > > +the value of max_comp_streams because single stream compression
> > > > > backend
> > > > > +implemented as a special case by lock overhead issue and does not
> > > > > support
> > > > > +dynamic max_comp_streams. Only multi stream backend supports dynamic
> > > > > +max_comp_streams adjustment.
> > > > >
> > > > > 3) Select compression algorithm
> > > > > Using comp_algorithm device attribute one can see available and
> > > > > diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> > > > > index 92a83df40a27..15fe6a27781b 100644
> > > > > --- a/drivers/block/zram/zcomp.c
> > > > > +++ b/drivers/block/zram/zcomp.c
> > > > > @@ -152,7 +152,7 @@ static void zcomp_strm_multi_release(struct zcomp
> > > > > *comp, struct zcomp_strm *zstr
> > > > > }
> > > > >
> > > > > /* change max_strm limit */
> > > > > -static int zcomp_strm_multi_set_max_streams(struct zcomp *comp, int
> > > > > num_strm)
> > > > > +static bool zcomp_strm_multi_set_max_streams(struct zcomp *comp, int
> > > > > num_strm)
> > > > > {
> > > > > struct zcomp_strm_multi *zs = comp->stream;
> > > > > struct zcomp_strm *zstrm;
> > > > > @@ -171,7 +171,7 @@ static int
> > > > > zcomp_strm_multi_set_max_streams(struct zcomp *comp, int num_strm)
> > > > > zs->avail_strm--;
> > > > > }
> > > > > spin_unlock(&zs->strm_lock);
> > > > > - return 0;
> > > > > + return true;
> > > > > }
> > > > >
> > > > > static void zcomp_strm_multi_destroy(struct zcomp *comp)
> > > > > @@ -231,10 +231,10 @@ static void zcomp_strm_single_release(struct
> > > > > zcomp *comp,
> > > > > mutex_unlock(&zs->strm_lock);
> > > > > }
> > > > >
> > > > > -static int zcomp_strm_single_set_max_streams(struct zcomp *comp, int
> > > > > num_strm)
> > > > > +static bool zcomp_strm_single_set_max_streams(struct zcomp *comp,
> > > > > int num_strm)
> > > > > {
> > > > > /* zcomp_strm_single support only max_comp_streams == 1 */
> > > > > - return -ENOTSUPP;
> > > > > + return 0;
> > > > > }
> > > >
> > > > IMHO, -ENOTSUPP for unsupported operation fits better than `false'.
> > > > yes, currently there are only two possible returns:
> > > > 0 -- success
> > > > -ENOTSUPP - not supported operation
> > > >
> > > > though, we can extend functions later and return additional codes, other
> > > > than `false' and `true'.
> > >
> > > Thing to expose to user isn't true and false but EINVAL.
> > >
> >
> > sure. I mean we can return actual zcomp_set_max_streams() error (if any)
> > back to user from max_comp_streams_store():
> >
> > [..]
> > ret = zcomp_set_max_streams(...);
> > [..]
> > return ret;
> >
> > > >
> > > > for example, -E2BIG if user requested extremly large
Re: [PATCH] zram: propagate error to user
Hello Sergey,
On Sun, Mar 09, 2014 at 07:58:51PM +0300, Sergey Senozhatsky wrote:
> Hello Minchan,
>
> On (03/07/14 18:51), Minchan Kim wrote:
> > Hello Sergey!
> >
> > On Fri, Mar 07, 2014 at 12:20:45PM +0300, Sergey Senozhatsky wrote:
> > > On (03/07/14 10:56), Minchan Kim wrote:
> > > > When we initialized zcomp with single, we couldn't change
> > > > max_comp_streams without zram reset but current interface doesn't
> > > > show any error to user and even it changes max_comp_streams's value
> > > > without any effect so it would make user very confusing.
> > > >
> > > > This patch prevents max_comp_streams's change when zcomp was
> > > > initialized as single zcomp and emit the error to user(ex, echo).
> > > >
> > > > Signed-off-by: Minchan Kim
> > > > ---
> > > > Documentation/blockdev/zram.txt | 9 +
> > > > drivers/block/zram/zcomp.c | 10 +-
> > > > drivers/block/zram/zcomp.h | 4 ++--
> > > > drivers/block/zram/zram_drv.c | 15 +++
> > > > 4 files changed, 23 insertions(+), 15 deletions(-)
> > > >
> > > > diff --git a/Documentation/blockdev/zram.txt
> > > > b/Documentation/blockdev/zram.txt
> > > > index 2604ffed51db..0595c3f56ccf 100644
> > > > --- a/Documentation/blockdev/zram.txt
> > > > +++ b/Documentation/blockdev/zram.txt
> > > > @@ -37,10 +37,11 @@ Note:
> > > > In order to enable compression backend's multi stream support
> > > > max_comp_streams
> > > > must be initially set to desired concurrency level before ZRAM device
> > > > initialisation. Once the device initialised as a single stream
> > > > compression
> > > > -backend (max_comp_streams equals to 0) changing the value of
> > > > max_comp_streams
> > > > -will not take any effect, because single stream compression backend
> > > > implemented
> > > > -as a special case and does not support dynamic max_comp_streams. Only
> > > > multi
> > > > -stream backend supports dynamic max_comp_streams adjustment.
> > > > +backend (max_comp_streams equals to 1), you will see error if you try
> > > > to change
> > > > +the value of max_comp_streams because single stream compression backend
> > > > +implemented as a special case by lock overhead issue and does not
> > > > support
> > > > +dynamic max_comp_streams. Only multi stream backend supports dynamic
> > > > +max_comp_streams adjustment.
> > > >
> > > > 3) Select compression algorithm
> > > > Using comp_algorithm device attribute one can see available and
> > > > diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> > > > index 92a83df40a27..15fe6a27781b 100644
> > > > --- a/drivers/block/zram/zcomp.c
> > > > +++ b/drivers/block/zram/zcomp.c
> > > > @@ -152,7 +152,7 @@ static void zcomp_strm_multi_release(struct zcomp
> > > > *comp, struct zcomp_strm *zstr
> > > > }
> > > >
> > > > /* change max_strm limit */
> > > > -static int zcomp_strm_multi_set_max_streams(struct zcomp *comp, int
> > > > num_strm)
> > > > +static bool zcomp_strm_multi_set_max_streams(struct zcomp *comp, int
> > > > num_strm)
> > > > {
> > > > struct zcomp_strm_multi *zs = comp->stream;
> > > > struct zcomp_strm *zstrm;
> > > > @@ -171,7 +171,7 @@ static int zcomp_strm_multi_set_max_streams(struct
> > > > zcomp *comp, int num_strm)
> > > > zs->avail_strm--;
> > > > }
> > > > spin_unlock(&zs->strm_lock);
> > > > - return 0;
> > > > + return true;
> > > > }
> > > >
> > > > static void zcomp_strm_multi_destroy(struct zcomp *comp)
> > > > @@ -231,10 +231,10 @@ static void zcomp_strm_single_release(struct
> > > > zcomp *comp,
> > > > mutex_unlock(&zs->strm_lock);
> > > > }
> > > >
> > > > -static int zcomp_strm_single_set_max_streams(struct zcomp *comp, int
> > > > num_strm)
> > > > +static bool zcomp_strm_single_set_max_streams(struct zcomp *comp, int
> > > > num_strm)
> > > > {
> > > > /* zcomp_strm_single support only max_comp_streams == 1 */
> > > > - return -ENOTSUPP;
> > > > + return 0;
> > > > }
> > >
> > > IMHO, -ENOTSUPP for unsupported operation fits better than `false'.
> > > yes, currently there are only two possible returns:
> > > 0 -- success
> > > -ENOTSUPP - not supported operation
> > >
> > > though, we can extend functions later and return additional codes, other
> > > than `false' and `true'.
> >
> > Thing to expose to user isn't true and false but EINVAL.
> >
>
> sure. I mean we can return actual zcomp_set_max_streams() error (if any)
> back to user from max_comp_streams_store():
>
> [..]
> ret = zcomp_set_max_streams(...);
> [..]
> return ret;
>
> > >
> > > for example, -E2BIG if user requested extremly large number of streams,
> > > like 5000 streams.
> >
> > I'm not sure it's right example for E2BIG.
> > When I read the comment, it says "argument list too long".
> > Anyway, when I tried ENOTSUPP, echo doesn't show meaningful error to user
> > and I dont' know it's casual
Re: [PATCH] zram: propagate error to user
Hello Minchan,
On (03/07/14 18:51), Minchan Kim wrote:
> Hello Sergey!
>
> On Fri, Mar 07, 2014 at 12:20:45PM +0300, Sergey Senozhatsky wrote:
> > On (03/07/14 10:56), Minchan Kim wrote:
> > > When we initialized zcomp with single, we couldn't change
> > > max_comp_streams without zram reset but current interface doesn't
> > > show any error to user and even it changes max_comp_streams's value
> > > without any effect so it would make user very confusing.
> > >
> > > This patch prevents max_comp_streams's change when zcomp was
> > > initialized as single zcomp and emit the error to user(ex, echo).
> > >
> > > Signed-off-by: Minchan Kim
> > > ---
> > > Documentation/blockdev/zram.txt | 9 +
> > > drivers/block/zram/zcomp.c | 10 +-
> > > drivers/block/zram/zcomp.h | 4 ++--
> > > drivers/block/zram/zram_drv.c | 15 +++
> > > 4 files changed, 23 insertions(+), 15 deletions(-)
> > >
> > > diff --git a/Documentation/blockdev/zram.txt
> > > b/Documentation/blockdev/zram.txt
> > > index 2604ffed51db..0595c3f56ccf 100644
> > > --- a/Documentation/blockdev/zram.txt
> > > +++ b/Documentation/blockdev/zram.txt
> > > @@ -37,10 +37,11 @@ Note:
> > > In order to enable compression backend's multi stream support
> > > max_comp_streams
> > > must be initially set to desired concurrency level before ZRAM device
> > > initialisation. Once the device initialised as a single stream
> > > compression
> > > -backend (max_comp_streams equals to 0) changing the value of
> > > max_comp_streams
> > > -will not take any effect, because single stream compression backend
> > > implemented
> > > -as a special case and does not support dynamic max_comp_streams. Only
> > > multi
> > > -stream backend supports dynamic max_comp_streams adjustment.
> > > +backend (max_comp_streams equals to 1), you will see error if you try to
> > > change
> > > +the value of max_comp_streams because single stream compression backend
> > > +implemented as a special case by lock overhead issue and does not support
> > > +dynamic max_comp_streams. Only multi stream backend supports dynamic
> > > +max_comp_streams adjustment.
> > >
> > > 3) Select compression algorithm
> > > Using comp_algorithm device attribute one can see available and
> > > diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> > > index 92a83df40a27..15fe6a27781b 100644
> > > --- a/drivers/block/zram/zcomp.c
> > > +++ b/drivers/block/zram/zcomp.c
> > > @@ -152,7 +152,7 @@ static void zcomp_strm_multi_release(struct zcomp
> > > *comp, struct zcomp_strm *zstr
> > > }
> > >
> > > /* change max_strm limit */
> > > -static int zcomp_strm_multi_set_max_streams(struct zcomp *comp, int
> > > num_strm)
> > > +static bool zcomp_strm_multi_set_max_streams(struct zcomp *comp, int
> > > num_strm)
> > > {
> > > struct zcomp_strm_multi *zs = comp->stream;
> > > struct zcomp_strm *zstrm;
> > > @@ -171,7 +171,7 @@ static int zcomp_strm_multi_set_max_streams(struct
> > > zcomp *comp, int num_strm)
> > > zs->avail_strm--;
> > > }
> > > spin_unlock(&zs->strm_lock);
> > > - return 0;
> > > + return true;
> > > }
> > >
> > > static void zcomp_strm_multi_destroy(struct zcomp *comp)
> > > @@ -231,10 +231,10 @@ static void zcomp_strm_single_release(struct zcomp
> > > *comp,
> > > mutex_unlock(&zs->strm_lock);
> > > }
> > >
> > > -static int zcomp_strm_single_set_max_streams(struct zcomp *comp, int
> > > num_strm)
> > > +static bool zcomp_strm_single_set_max_streams(struct zcomp *comp, int
> > > num_strm)
> > > {
> > > /* zcomp_strm_single support only max_comp_streams == 1 */
> > > - return -ENOTSUPP;
> > > + return 0;
> > > }
> >
> > IMHO, -ENOTSUPP for unsupported operation fits better than `false'.
> > yes, currently there are only two possible returns:
> > 0 -- success
> > -ENOTSUPP - not supported operation
> >
> > though, we can extend functions later and return additional codes, other
> > than `false' and `true'.
>
> Thing to expose to user isn't true and false but EINVAL.
>
sure. I mean we can return actual zcomp_set_max_streams() error (if any)
back to user from max_comp_streams_store():
[..]
ret = zcomp_set_max_streams(...);
[..]
return ret;
> >
> > for example, -E2BIG if user requested extremly large number of streams,
> > like 5000 streams.
>
> I'm not sure it's right example for E2BIG.
> When I read the comment, it says "argument list too long".
> Anyway, when I tried ENOTSUPP, echo doesn't show meaningful error to user
> and I dont' know it's casual err number for userspace.
> Pz, comment about that.
>
E2BIG (introduced by POSIX.1-2001) was a quick example and, probably, not
the perfect one. In general, I'm not against this change and I can live
with zcomp_set_max_streams() returning bool.
-ss
> >
> > >
> > > static void zcomp_strm_single_destroy(struct zcomp *comp)
> > > @@ -283,7 +283,7 @@ ssize_t zcomp_available
Re: [PATCH] zram: propagate error to user
Hello Sergey!
On Fri, Mar 07, 2014 at 12:20:45PM +0300, Sergey Senozhatsky wrote:
> On (03/07/14 10:56), Minchan Kim wrote:
> > When we initialized zcomp with single, we couldn't change
> > max_comp_streams without zram reset but current interface doesn't
> > show any error to user and even it changes max_comp_streams's value
> > without any effect so it would make user very confusing.
> >
> > This patch prevents max_comp_streams's change when zcomp was
> > initialized as single zcomp and emit the error to user(ex, echo).
> >
> > Signed-off-by: Minchan Kim
> > ---
> > Documentation/blockdev/zram.txt | 9 +
> > drivers/block/zram/zcomp.c | 10 +-
> > drivers/block/zram/zcomp.h | 4 ++--
> > drivers/block/zram/zram_drv.c | 15 +++
> > 4 files changed, 23 insertions(+), 15 deletions(-)
> >
> > diff --git a/Documentation/blockdev/zram.txt
> > b/Documentation/blockdev/zram.txt
> > index 2604ffed51db..0595c3f56ccf 100644
> > --- a/Documentation/blockdev/zram.txt
> > +++ b/Documentation/blockdev/zram.txt
> > @@ -37,10 +37,11 @@ Note:
> > In order to enable compression backend's multi stream support
> > max_comp_streams
> > must be initially set to desired concurrency level before ZRAM device
> > initialisation. Once the device initialised as a single stream compression
> > -backend (max_comp_streams equals to 0) changing the value of
> > max_comp_streams
> > -will not take any effect, because single stream compression backend
> > implemented
> > -as a special case and does not support dynamic max_comp_streams. Only multi
> > -stream backend supports dynamic max_comp_streams adjustment.
> > +backend (max_comp_streams equals to 1), you will see error if you try to
> > change
> > +the value of max_comp_streams because single stream compression backend
> > +implemented as a special case by lock overhead issue and does not support
> > +dynamic max_comp_streams. Only multi stream backend supports dynamic
> > +max_comp_streams adjustment.
> >
> > 3) Select compression algorithm
> > Using comp_algorithm device attribute one can see available and
> > diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> > index 92a83df40a27..15fe6a27781b 100644
> > --- a/drivers/block/zram/zcomp.c
> > +++ b/drivers/block/zram/zcomp.c
> > @@ -152,7 +152,7 @@ static void zcomp_strm_multi_release(struct zcomp
> > *comp, struct zcomp_strm *zstr
> > }
> >
> > /* change max_strm limit */
> > -static int zcomp_strm_multi_set_max_streams(struct zcomp *comp, int
> > num_strm)
> > +static bool zcomp_strm_multi_set_max_streams(struct zcomp *comp, int
> > num_strm)
> > {
> > struct zcomp_strm_multi *zs = comp->stream;
> > struct zcomp_strm *zstrm;
> > @@ -171,7 +171,7 @@ static int zcomp_strm_multi_set_max_streams(struct
> > zcomp *comp, int num_strm)
> > zs->avail_strm--;
> > }
> > spin_unlock(&zs->strm_lock);
> > - return 0;
> > + return true;
> > }
> >
> > static void zcomp_strm_multi_destroy(struct zcomp *comp)
> > @@ -231,10 +231,10 @@ static void zcomp_strm_single_release(struct zcomp
> > *comp,
> > mutex_unlock(&zs->strm_lock);
> > }
> >
> > -static int zcomp_strm_single_set_max_streams(struct zcomp *comp, int
> > num_strm)
> > +static bool zcomp_strm_single_set_max_streams(struct zcomp *comp, int
> > num_strm)
> > {
> > /* zcomp_strm_single support only max_comp_streams == 1 */
> > - return -ENOTSUPP;
> > + return 0;
> > }
>
> IMHO, -ENOTSUPP for unsupported operation fits better than `false'.
> yes, currently there are only two possible returns:
> 0 -- success
> -ENOTSUPP - not supported operation
>
> though, we can extend functions later and return additional codes, other
> than `false' and `true'.
Thing to expose to user isn't true and false but EINVAL.
>
> for example, -E2BIG if user requested extremly large number of streams,
> like 5000 streams.
I'm not sure it's right example for E2BIG.
When I read the comment, it says "argument list too long".
Anyway, when I tried ENOTSUPP, echo doesn't show meaningful error to user
and I dont' know it's casual err number for userspace.
Pz, comment about that.
>
> >
> > static void zcomp_strm_single_destroy(struct zcomp *comp)
> > @@ -283,7 +283,7 @@ ssize_t zcomp_available_show(const char *comp, char
> > *buf)
> > return sz;
> > }
> >
> > -int zcomp_set_max_streams(struct zcomp *comp, int num_strm)
> > +bool zcomp_set_max_streams(struct zcomp *comp, int num_strm)
> > {
> > return comp->set_max_streams(comp, num_strm);
> > }
> > diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
> > index 8b8997f8613b..c59d1fca72c0 100644
> > --- a/drivers/block/zram/zcomp.h
> > +++ b/drivers/block/zram/zcomp.h
> > @@ -46,7 +46,7 @@ struct zcomp {
> >
> > struct zcomp_strm *(*strm_find)(struct zcomp *comp);
> > void (*strm_release)(struct zcomp *comp, struct zcomp_strm *zstrm);
> > - int (*set_max_streams)(str
Re: [PATCH] zram: propagate error to user
On (03/07/14 10:56), Minchan Kim wrote:
> When we initialized zcomp with single, we couldn't change
> max_comp_streams without zram reset but current interface doesn't
> show any error to user and even it changes max_comp_streams's value
> without any effect so it would make user very confusing.
>
> This patch prevents max_comp_streams's change when zcomp was
> initialized as single zcomp and emit the error to user(ex, echo).
>
> Signed-off-by: Minchan Kim
> ---
> Documentation/blockdev/zram.txt | 9 +
> drivers/block/zram/zcomp.c | 10 +-
> drivers/block/zram/zcomp.h | 4 ++--
> drivers/block/zram/zram_drv.c | 15 +++
> 4 files changed, 23 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
> index 2604ffed51db..0595c3f56ccf 100644
> --- a/Documentation/blockdev/zram.txt
> +++ b/Documentation/blockdev/zram.txt
> @@ -37,10 +37,11 @@ Note:
> In order to enable compression backend's multi stream support
> max_comp_streams
> must be initially set to desired concurrency level before ZRAM device
> initialisation. Once the device initialised as a single stream compression
> -backend (max_comp_streams equals to 0) changing the value of max_comp_streams
> -will not take any effect, because single stream compression backend
> implemented
> -as a special case and does not support dynamic max_comp_streams. Only multi
> -stream backend supports dynamic max_comp_streams adjustment.
> +backend (max_comp_streams equals to 1), you will see error if you try to
> change
> +the value of max_comp_streams because single stream compression backend
> +implemented as a special case by lock overhead issue and does not support
> +dynamic max_comp_streams. Only multi stream backend supports dynamic
> +max_comp_streams adjustment.
>
> 3) Select compression algorithm
> Using comp_algorithm device attribute one can see available and
> diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> index 92a83df40a27..15fe6a27781b 100644
> --- a/drivers/block/zram/zcomp.c
> +++ b/drivers/block/zram/zcomp.c
> @@ -152,7 +152,7 @@ static void zcomp_strm_multi_release(struct zcomp *comp,
> struct zcomp_strm *zstr
> }
>
> /* change max_strm limit */
> -static int zcomp_strm_multi_set_max_streams(struct zcomp *comp, int num_strm)
> +static bool zcomp_strm_multi_set_max_streams(struct zcomp *comp, int
> num_strm)
> {
> struct zcomp_strm_multi *zs = comp->stream;
> struct zcomp_strm *zstrm;
> @@ -171,7 +171,7 @@ static int zcomp_strm_multi_set_max_streams(struct zcomp
> *comp, int num_strm)
> zs->avail_strm--;
> }
> spin_unlock(&zs->strm_lock);
> - return 0;
> + return true;
> }
>
> static void zcomp_strm_multi_destroy(struct zcomp *comp)
> @@ -231,10 +231,10 @@ static void zcomp_strm_single_release(struct zcomp
> *comp,
> mutex_unlock(&zs->strm_lock);
> }
>
> -static int zcomp_strm_single_set_max_streams(struct zcomp *comp, int
> num_strm)
> +static bool zcomp_strm_single_set_max_streams(struct zcomp *comp, int
> num_strm)
> {
> /* zcomp_strm_single support only max_comp_streams == 1 */
> - return -ENOTSUPP;
> + return 0;
> }
IMHO, -ENOTSUPP for unsupported operation fits better than `false'.
yes, currently there are only two possible returns:
0 -- success
-ENOTSUPP - not supported operation
though, we can extend functions later and return additional codes, other
than `false' and `true'.
for example, -E2BIG if user requested extremly large number of streams,
like 5000 streams.
>
> static void zcomp_strm_single_destroy(struct zcomp *comp)
> @@ -283,7 +283,7 @@ ssize_t zcomp_available_show(const char *comp, char *buf)
> return sz;
> }
>
> -int zcomp_set_max_streams(struct zcomp *comp, int num_strm)
> +bool zcomp_set_max_streams(struct zcomp *comp, int num_strm)
> {
> return comp->set_max_streams(comp, num_strm);
> }
> diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
> index 8b8997f8613b..c59d1fca72c0 100644
> --- a/drivers/block/zram/zcomp.h
> +++ b/drivers/block/zram/zcomp.h
> @@ -46,7 +46,7 @@ struct zcomp {
>
> struct zcomp_strm *(*strm_find)(struct zcomp *comp);
> void (*strm_release)(struct zcomp *comp, struct zcomp_strm *zstrm);
> - int (*set_max_streams)(struct zcomp *comp, int num_strm);
> + bool (*set_max_streams)(struct zcomp *comp, int num_strm);
> void (*destroy)(struct zcomp *comp);
> };
>
> @@ -64,5 +64,5 @@ int zcomp_compress(struct zcomp *comp, struct zcomp_strm
> *zstrm,
> int zcomp_decompress(struct zcomp *comp, const unsigned char *src,
> size_t src_len, unsigned char *dst);
>
> -int zcomp_set_max_streams(struct zcomp *comp, int num_strm);
> +bool zcomp_set_max_streams(struct zcomp *comp, int num_strm);
> #endif /* _ZCOMP_H_ */
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
>
